1. Field
The subject matter disclosed herein relates to wireless communication systems, and more specifically, to position determination methods and apparatuses for use with and/or by wireless mobile stations.
2. Information
GPS and other like satellite positioning systems have enabled navigation services for mobile handsets in outdoor environments. Since satellite signals may not be reliably received or acquired in an indoor environment, different techniques may be employed to enable navigation services. For example, mobile stations may obtain a position fix by measuring ranges to three or more terrestrial wireless access points that are positioned at known locations. Such ranges may be measured, for example, by obtaining a MAC ID address from signals received from such access points and obtaining range measurements to the access points by measuring one or more characteristics of signals received from such access points such as, for example, signal strength and round trip delay.
A navigation system may provide navigation assistance or mapped features to a mobile station as it enters a particular area. For example, in some implementations, an indoor navigation system may selectively provide assistance information to mobile stations to facilitate and/or enable location services. Such assistance information may include, for example, information to facilitate measurements of ranges to wireless access points at known fixed locations. For example, “radio context parameter map” data indicating expected received-signal-strength-indicator (RSSI) or round-trip time (RTT) values associated with access points may enable a mobile station to associate signal measurements with locations in an indoor area. By matching measured RSSI or RTT values of acquired signals marked with particular MAC IDs with the RSSI or RTT values expected for signals marked by these particular MAC IDs at a specific location, the location of the receiver may be inferred to be at the specific location.